Coil for absorption refrigeration apparatus



Get. 21, 1969 B. R. REISTAD 3,473,346

COIL FOR ABSORPTION REFRIGERATION APPARATUS Original Filed March 27,1964 3 Sheets-Shed FIG. I

Lwm rox.

MM WWW Oct. 21, 1969 a. R. REISTAD 3,473,346

COIL FOR ABSORPTION REFRIGERATION APPARATUS Original Filed March 2'7,1964 3 Sheets-Sheet Shape of 1%: W Iva/72 era 1 Ez'glf W 7 5 ##0/9/1 lpipe parfz bm y M Get. 21, 1969 B. R. RElSTAD 3,473,346

COIL FOR ABSORPTION REFRIGERATION APPARATUS Original Filed March 2'7,1964 3 Sheets-Sheet E WWW WWW

United States Patent US. Cl. 62--476 Claims ABSTRACT OF THE DISCLOSUREAbsorption refrigeration apparatus having a circuit for inert gasincluding a coil formed of ferrous metal having horizontally extendingstraight pipe sections of cylindrical form and connecting bends and aninlet at one elevaticn and an outlet at a lower elevation, at least onebend being formed of piping having a minor axis and a longer major axis,the longer major axis extending vertically in the same general directionas the axis of the radius of curvature of the bend, the inner side ofthe bend at one side of its longer major axis having a longitudinalreentrant portion which extends toward the opposite outer side of thebend, the inner extremity of the reentrant portion contacting andabutting the opposite outer side of the bend, and the straight pipingsections connected to the bend each having an inner diameter equal tothe vertical distance between the top and bottom of the opposing wallsof the piping at the bend at the vicinity of its longer major axis.

This application is a division of my application Ser. No. 355,337, filedMar. 27, 1964, for Method of Making Coil for Absorption RefrigerationApparatus, now Patent No. 3,348,402 granted Oct. 24, 1967.

BRIEF SUMMARY OF THE INVENTION My invention relates to a coil forabsorption refrigeration apparatus, and more particularly to evaporatorand absorber coils for absorption refrigeration apparatus of the inertgas type.

It is an object of my invention to provide an improved coil of this typewhich includes straight portions and connecting bends having small radiiof curvature, whereby a maximum number of straight coil portions may beprovided in a space of a given size.

Another object of the invention is to provide an improved coil of thistype which includes two banks of straight portions spaced from oneanother and connecting bends having small radii of curvature, wherebythe space between the two banks of straight portions will be at aminimum.

A further object of my invention is to provide an improved coil of thistype which is formed of piping or tubing of cylindrical form andincludes at least one bend which is non-circular in cross-section andhas a reentrant part at a first side wall at the inner side of the bendwhich functions as a support for the opposite second side wall at theouter side of the bend, the straight pipe sections con nected to thebend each having an inner diameter substantially equal to the distancebetween the inner surfaces of the opposing walls of the piping at thebend at the immediate vicinity of its major axis.

"ice

The above and other objects and advantages of my invention will bebetter understood from the following description taken in connectionwith the accompanying drawing forming a part of the specification.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING FIG. 1 is a viewmore or less diagrammatically illustrating an absorption refrigerationapparatus of the inert gas type to which the invention has been applied;

FIG. 2 is a fragmentary vertical sectional view of a refrigerator and anevaporator therefor which embodies the invention and is associated withrefrigeration apparatus like that shown in FIG. 1;

FIG. 3 is a horizontal sectional view taken at line 3-3 of FIG. 2 toillustrate the evaporator more clearly and also an absorber whichembodies the invention;

FIG. 4 is a fragmentary vertical sectional view taken at line 4-4 ofFIG. 2;

FIG. 5 is a fragmentary vertical sectional view taken at line 55 of FIG.3;

FIGS. 6 and 7 are diagrammatic views illustrating the manner in whichthe bends are formed in a bending machine; and

FIGS. 8 and 9 are vertical sectional views taken at lines 88 and 9--9,respectively, of FIG. 7.

DETAILED DESCRIPTION In FIG. 1 I have shown absorption refrigerationapparatus of a uniform pressure type which is well known in the art andin which an inert pressure equalizing gas is employed. Such arefrigeration apparatus comprises a generator or boiler 10 containing arefrigerant, such as ammonia, in solution in a body of absorptionliquid, such as water. Heat may be supplied to the boiler 10 from aheating tube or flue 11 thermally connected therewith, as by welding.The heating tube 11 may be heated in any suitable manner, as by a liquidor gaseous fuel burner 12, for example, which is adapted to project itsflame into the lower end of the tube.

The heat supplied to the boiler 10 and its contents expels refrigerantvapor out of solution, and the vapor thus generated flows through aconduit 14 to an air-cooled condenser 15 in which it is condensed andliquefied. Liquid refrigerant flows from condenser 15 through a conduit16 into an evaporator 17 in which it evaporates and diffuses into aninert pressure equalizing gas, such as hydrogen, which enters the upperpart thereof through a conduit 18. Due to evaporation of refrigerantfluid into inert gas, a refrigerating effect is produced and heat isabstracted from the surroundings.

The rich gas mixture of refrigerant vapor and inert gas formed inevaporator 17 flows from the lower part thereof through a conduit 19 andabsorber vessel 21 into the lower part of an absorber coil 21. Inabsorber coil 21 the rich gas mixture flows countercurrent to downwardlyflowing absorption liquid which enters through a conduit 22. Theabsorption liquid absorbs refrigerant vapor from inert gas, and inertgas weak in refrigerant flows from the upper part of absorber coil 21through conduit 18 into the upper part of cooling element 16.

The circulation of gas in the gas circuit just described is due to thedifference in specific weight of the columns of gas rich and weak,respectively, in refrigerant vapor. Since the column of gas rich inrefrigerant vapor and flowing from the evaporator 17 to the absorbercoil 21 is heavier than the column of gas weak in refrigerant vapor andflowing from absorber coil 21 to the evaporator 17, a force is producedor developed within the apparatus for causing circulation of gas in themanner described.

Absorption solution flows downward through coil 21 into the absorbervessel 20, and such solution, which is enriched in refrigerant, passesfrom the vessel through a conduit 23 and an inner passage or pipe 24 ofliquid heat exchanger 25 into the lower end of a vapor lift pipe or tube26 which is in thermal exchange relation with the heating tube 11, as bywelding. Liquid is raised by vaporliquid lift action through pipe 26into the upper part of boiler 10. Refrigerant vapor expelled out ofsolution in boiler 10, together with refrigerant vapor entering throughpipe 26, flows upward from the boiler through the conduit 14 to thecondenser 15, as previously explained.

The outlet end of condenser 15 is connected by an upper extension ofconduit 16 and a conduit 27 to a part of the gas circuit, as to theupper part of conduit 19, for example, so that any inert gas which maypass through the condenser 14 can flow into the gas circuit. Theabsorption liquid from which refrigerant vapor has been expelled flowsfrom the boiler through a connection 28, an outer pipe or passage 29 ofthe liquid heat exchanger 25 and conduit 22 into the upper part of theabsorber coil 21. The circulation of absorption solution in the liquidcircuit just described is effected by raising of liquid through pipe 26.

In order to effect heat exchange between inert gas which is weak inrefrigerant and flowing to the evaporator 17 through the conduit 18 andinert gas which is rich in refrigerant and flowing from the evaporator17 through the conduit 19, the conduits 18 and 19 may be heatconductively connected to one another at 30 in any suitable manner.Also, the conduit 16 through which liquid refrigerant flows from thecondenser to the evaporator 17 may be heat conductivley connected at 31to the conduit 19 through which inert gas rich in refrigerant flows tothe absorber vessel 20, thereby cooling the liquid refrigerant before itiis introduced into the evaporator 17.

While the evaporator 17 in FIG. 1 is diagrammatically shown in the formof a vertical looped coil, a practical form of such a cooling elementmay be an arrangement in which the looped coil is disposed substantiallyin a single horizontal plane across the space to be cooled. Such apractical embodiment is shown in FIGS. 2 and 3 in which parts similar tothose shown in FIG. 1 are designated by the same reference numerals.

The evaporator 17 in FIGS. 2 and 3 comprises a looped coil which isdisposed substantially in a single horizontal plane and adapted toextend from one lateral side wall 32 to the opposite lateral side wall32 of a thermally insulated storage compartment 33 of a refrigeratorcabinet 34 provided with a door 35 hinged at 36 to the front of thecabinet. The thermally insulated walls defining the storage compartment33 include a rear insulated wall 37 having an opening and a removableenclosure member 38 therefor and through which the evaporator 17 isadapted to be inserted into the insulated interior of the cabinet 34.The parts of the conduits 18 and 19 heat conductively connected to oneanother at 30 and the part of the liquid refrigerant conduit 16 heatconductively connected to the conduit 19 at 31 may be disposed withinthe closure member 38 and retained therein within a body of insulation.

In FIGS. 2 and 3 the boiler 10, absorber vessel 20, absorber 21 andcondenser 15 are disposed in a vertically extending apparatus space 39at the rear of the refrigerator cabinet 34. The parts of the boiler 10are F embedded in insulation retained within a shell 40, the heatingtube 11 projecting through openings in the top and bottom, respectively,of the shell. Upward circulation of air is induced by natural draft inthe compartment 39 which defines a vertically extending flue, and h suchupward movement of air effects cooling of the absorber coil 21 at onelevel and the condenser 15 located at a higher level.

As shown in FIGS. 2 and 3, the evaporator 17 is heat conductivelyconnected in any suitable manner to the underside of a horizontallydisposed plate 41. The plate 41 which is positioned closely adjacent toand at the vicinity of the ceiling 42 of the storage compartment 33,extends substantially over the entire width or the storage compartment33 and from the rear insulated wall 37 to a region 43 at the open frontwhich is relatively close to the rear face of the door to divide thecompartment 33 into upper and lower spaces 33a and 33b, respectively.

The evaporator 17, which is adapted to be operated below the freezingtemperature of water, is employed to abstract heat from the plate 41which constitutes the bottom of the upper space 33a which functions asthe freezing section of the refrigerator. The plate 41 and evaporator 17in thermal exchange therewith also are employed to effect cooling of airin the lower space 33b of the storage compartment 33 which flows inthermal exchange relation therewith. Hence, the plate 41 has a limitedheat transfer surface which is employed to effect cooling of air in thebottom space 33b of the storage compartment 33.

The parts of the absorption refrigeration apparatus shown in FIGS. 2 and3 and just described, whose relative positions are substantially fixed,usually are formed of iron or steel when ammonia and water are employedas the refrigerant and liquid absorbent, respectively. Therefore, thepiping for the evarporator 17 and absorber 21, which are connected byconduits to other parts of the refrigeration apparatus and form aunitary part thereof, are formed of such ferrous metal having relativelythick walls. As best shown in FIG. 3, the looped coil forming theevaporator 17 includes straight sections 17a and connecting bends 17b;and the looped coil forming the absorber 21 includes straight sections21a and connecting bends 21b.

In accordance with my invention, in order to provide evaporator andabsorber coils having straight portions connected by bends having smallradii of curvature, the piping forming the bends of the coils isnon-circular in cross-section with a minor axis and longer major axiswhich is substantially parallel to the axes of the bends, whereby amaximum number of straight coil sections or portions may be disposed ina space of a given size. As shown in FIG. 4, the bends 17b of theevaporator coil 17 are formed of piping which is non-circular incross-section and has the shape of the numeral eight with the top andbottom parts of annular form and a narrow neck part 17d therebetween.

As seen in FIG. 4, the bends 17b of the evaporator coil 17 havehorizontal minor axes and longer vertical major axes 17e17e which areparallel to the axes of the radii of curvature of the bends. The narrowneck parts 17d of the bends 17b are formed by reentrant portions 17 and17g at the longer vertical side walls of the piping, the innerextremities of which contact and abut one another. Hence, the major axis17e17e of each bend 17b extends substantially in the same direction asthe axis of the radius of curvature of the bend.

As seen in FIG. 5, the bends 21b of the absorber coil '21 also arenon-circular in cross-section and have the shape of the numeral eightwith top and bottom parts 210 and narrow connecting neck parts 21dtherebetween. The longer vertical major axes 21e21e of the bends 21b areparallel to the axes of the radii of curvature of the bends. Hence, themajor axis 21e21e of each bend 21b extends substantially in the samedirection as the axis of the radius of curvature of the bend. Also, theneck parts 21d are formed by reentrant portions 21] and 21g at thelonger vertical sides of the piping, the inner extremities of whichcontact and abut one another. The straight portions 17a of theevaporator coil 17 are of cylindrical form and have inner diameters Dsubstantially equal to the distance D between the inner surfaces of thetop and bottom opposing walls of the coil 17 at the connecting bends 17bat the immediate vicinities of the major axes 17e17e thereof, as shownin FIG. 4. Likewise, the straight portions 21a of the absorber coil 21are of cylindrical form and have inner diameters D substantially equalto the distance D between the inner surfaces of the top and bottomopposing walls of the coil 21 at the connecting bends 21a at theimmediate vicinities of the major axes 21e--21e thereof, as shown inFIG. 5.

By providing evaporator and absorber coils 17 and 21 formed with bends17b and 21b of the kind just described and shown in FIGS. 4 and 5, agreater number of coil straight sections can be employed in a givenspace than otherwise would be possible. This is so because the bends 17band 21b can be formed with smaller radii of curvature than the bendsthat could be formed from the piping which is cylindrical incross-section and provide the straight sections of the coils. Byproviding the bends 17b for the evaporator coil 17 in FIG. 3, forexample, a maximum number of straight pipe sections 17a can be employedalongside one another in heat conductive relation with the underside ofthe plate 41. In this way a longer path of flow for the liquidrefrigerant can be provided at the underside of the plate 41 whereby therefrigerating efiect produced due to evaporation of refrigerant fluidinto inert gas is increased.

I make the evaporator and absorber coils 17 and 21 by deforming into theshape of the numeral eight 1ongitudinally spaced regions of ferrouspiping which is cylindrical in cross-section. After straight lengths ofpiping are deformed at regions at which the bends of the piping are tobe formed, the piping is positioned in a suitable pipe bending machinehaving a pivot 44, a pair of back-up rollers 45, and a roller 46 whichis mounted for movement on an arm in any suitable manner (not shown) tobend the piping. The roller 46 is shown in one position in FIG. 6 aftera bend is partly made and in another position in FIG. 7 after the bendis completed.

As shown in FIG. 8, the roller 46 is formed with an outer peripheralwall 46a having the shape of the outer vertical side of the pipingagainst which it bears. However, the outer peripheral wall 44a of thepivot 44, which bears against the inner vertical side of the piping, isessentially straight, as shown in FIG. 9. Accordingly, after the bend isformed the roller 46 can be retracted from the position shown in FIG. 7and the bend just formed can be removed from the pivot 44 by a simplelifting movement.

As shown in FIGS. 7 and 8, the axis of the radius of curvature of thebend is parallel to the major axis 17e-- 17e of the region of the pipingdeformed into the shape of the numeral eight. While the bend is beingformed, the reentrant portion 17 at the inner side wall of the pipingfunctions as a support against which the reentrant portion 17g at theouter side wall of the piping bears. This enables the bends in theevaporator and absorber coils 17 and 21 to be formed by cold bendingwithout the necessity of heating the piping before or during the bendingoperation. By first deforming longitudinally spaced regions in suitableapparatus to provide piping sections having opposed reentrant portionsin the longer side walls thereof, the deformed regions offer lessresistance to bending than the piping of circular cross-section beforeit was deformed.

When the deformed region of the piping is being bent, the outer sidewall thereof is subjected to tensile forces and the inner side wallthereof is subjected to compressive forces. The magnitude of the tensileand compressive forces developed in piping when it is being bent and theability of the piping to withstand these forces without localizedbuckling is dependent upon the ratio of the diameter of the piping tothe radius of curvature of the bend.

By deforming the piping in the manner shown in FIGS. 4 and 5 at theregions at which the bends are to be formed, the effective diameter ofthe piping is reduced for the bending operation without undulydecreasing the overall cross-sectional area of the piping at the bends.

In absorption refrigeration apparatus of the inert gas type a force isproduced within the apparatus for causing circulation of gas through andbetween the evaporator 17 and absorber 21, as explained above. In theevent the deforming of the piping by providing opposed reentrantportions at the longer side walls thereof reduces the overallcross-section of the piping to such an extent that the circulation ofgas in the gas circuit will be impaired, it may be desirable to selectpiping for the evaporator and absorber coils of such size that, afterforming bends in the coils in the manner shown and described above, theover all cross-sectional areas at the bends of the coils will besufficiently large not to impair operation of the refrigerationapparatus.

It will thus be seen that I have provided an improved evaporator andabsorber formed by coils having straight portions and connecting bendsand an inlet and outlet for inert gas at different elevations. Byproviding the reentrant portions at the opposing longer side walls ofthe piping with their inner extremities contacting and abutting oneanother, the inner side wall of the piping effectively functions tosupport the outer side wall during the bending operation. Although thepiping of the evaporator coil 17 is deformed to provide the bends 17b,the height of the piping at the bends is not changed to such an extentthat it will adversely affect the downward flow of liquid refrigerantthrough the coil by gravity.

By providing bends 21b for the absorber coil 21 having small radii ofcurvature in accordance with my invention the two banks of the straightsections 21a of the coil will 'be closer to one another so that thedepth of the apparatus space 39 can be reduced. Moreover, by providingbends 21b which not only have small radii of curvature but also areinclined downward, the absorber coil 21 can be formed with straightsections 21a which are essentially horizontal, whereby a greater numberof straight pipe sections can be employed in an absorber coil of a givenheight than in an absorber coil where the straight pipe sections andbends are both inclined to the horizontal.

I claim:

1. Absorption refrigeration apparatus of the class described having, incombination, a circuit for gas including a coil formed of ferrous metalhaving straight portions and connecting bends, and an inlet and outletat different elevations, the straight portions of said coil beingcircular in cross-section, at least one bend of said coil beingnoncircular in cross-section and having a minor axis and a longer majoraxis which extends substantially in the same direction as the axis ofthe radius of curvature of said one bend, and the straight portions ofsaid coil connected to said one bend each having an inner diametersubstantially equal to the distance between the inner surfaces of theopposing walls of said coil at said one bend at the immediate vicinityof said major axis thereof.

2. Apparatus as set forth in claim 1 in which said noncircular bend ofsaid coil comprises piping having a longitudinal reentrant portion atone side of the major axis thereof which extends toward the oppositeside of said piping, the inner extremity of said reentrant portioncontacting and abutting the opposite side of said piping.

3. Apparatus as set forth in claim 1 in which said longitudinalreentrant portion at one side of the major axis of said piping is at theinner side of said one bend and extends toward the opposite outer sideof said one bend, the inner extremity of said reentrant portioncontacting and abutting the opposite outer side of said one bend.

4. Apparatus as set forth in claim 3 in which said longitudinalreentrant portion at the inner side of said one bend functions as afirst longitudinal reentrant portion and said piping at the oppositeside of the major axis thereof and at the outer side of said one bendhas a second longitudinal reentrant portion which extends toward theinner side of said one bend, the inner extremities of said first andsecond reentrant portions contacting and abutting one another.

5. Apparatus as set forth in claim 1 in which said one bend of said coilcomprises piping having the shape of the numeral eight in cross-sectionwith adjacent parts 10 of annular form and a contracted necktherebetween, the longer major axis passing through the contracted neckportion and bisecting the parts of annular forrn.

References Cited UNITED STATES PATENTS LLOYD L. KING, Primary ExaminerUS. Cl. X.R.

